Alert archive / Wisconsin / Mesoscale Discussions in 2020
Mesoscale Discussion 1713
The Storm Prediction Center issued this mesoscale discussion at Sep 25, 2020, 5:31 PM CDT for Gogebic County, Houghton County, Ontonagon County, Michigan; 4 counties in Wisconsin. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- Sep 25, 2020, 5:31 PM CDT (22:31 UTC)
- Expired
- Sep 25, 2020, 7:30 PM CDT
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Gogebic County, MI, Houghton County, MI, Ontonagon County, MI, Ashland County, WI, Bayfield County, WI, Iron County, WI, Sawyer County, WI
The radar
The Duluth radar (KDLH), 143 km from the middle of the area, began a volume at 22:31 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Green Bay/Straub, WI (KGRB), launched 12:00Z, 10.5 hours before the alert went out and 281 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1130 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 14 m²/s²
- 0-3 km storm-relative helicity
- 6 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
099 ACUS11 KWNS 252231 SWOMCD SPC MCD 252231 MIZ000-WIZ000-260030- Mesoscale Discussion 1713 NWS Storm Prediction Center Norman OK 0531 PM CDT Fri Sep 25 2020 Areas affected...Western Upper Michigan/Wisconsin border vicinity Concerning...Severe potential...Watch possible Valid 252231Z - 260030Z Probability of Watch Issuance...40 percent SUMMARY...Increasing thunderstorm development, including the evolution of one or two supercells, appears possible near or just west of the Ironwood MI area by 6-7 PM CDT. This may include potential for a tornado or two, in addition to large hail, if stronger storm development is maintained along or just south of the surface frontal zone. Some uncertainty lingers, but trends are being monitored for the possibility of a severe weather watch. DISCUSSION...Latest model output remains suggestive that large-scale forcing for ascent, associated with lower/mid tropospheric warm advection, may contribute to increasing thunderstorm development in the vicinity of a stalled frontal zone near the southern Lake Superior shore during the next few hours. It appears that this may be aided by a focused area of strengthening divergence aloft, ahead of an approaching low amplitude short wave trough, perhaps associated with a coupling of 50-60 kt westerly 500 mb speed maxima. Coinciding with the northeastward migration of a surface low across the Hayward WI area. toward the Ironwood MI vicinity, a southwesterly 850 mb jet is forecast to strengthen from 30-40 kt. contributing to sizable clockwise-curved low-level hodographs within the warm sector of the low. Beneath the nose of an east-northeastward advecting plume of warm, elevated mixed-layer air, and relatively cool mid/upper-levels, modest boundary-layer dew points in the lower 60s appear to be contributing to mixed-layer CAPE on the order of 1000-1500 J/kg. Near the vicinity of the surface frontal zone, the environment may become conducive to the evolution of one or two supercells, capable of producing large hail and posing potential to produce a tornado, before activity possibly consolidates into an organizing cluster later this evening. ..Kerr/Hart.. 09/25/2020 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MQT...GRB...DLH... LAT...LON 46539171 47388828 46228887 45889056 45849159 46539171
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 25, 6:01 PM CDT | Severe Thunderstorm Watch | SPC | Gogebic, Houghton, Keweenaw, Ontonagon | 4 hr |
Nearby
Mesoscale Discussions in Wisconsin, 2020Mesoscale Discussions in Michigan, 2020Every mesoscale discussion in 2020
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.